New Mexico Mineral Symposium — Abstracts

In 1980 Joe Taggart and Eugene Foord identified austinite, beta-duftite, and conichalcite from Tucker's tunnel in Hinsdale County, Colorado. In 1981 Nick Theis and Mike Madson discovered what turned out to be a new mineral at this locality. Material was sent to Sid Williams for analysis, and he identified the new mineral theisite, along with several other minerals. The other minerals were adamite, anglesite, azurite, barite, calcite, cerussite, chalcocite, chrysocolla, covellite, cuprite, duftite, galena, hemimorphite, kolwezite, malachite, partzite, quartz, sphalerite, tenorite, tetrahedrite, uraninite, and zeunerite.

Later investigations by Robert Cobban and Jack Murphy found the mineral aurichalcite. More recently, the author has collected numerous samples and sent some of them to Paul Hlava for
analysis. This work has resulted in the addition of still more species. These include cinnabar, olivenite, tennantite, and willemite. This brings the species tally up to 30.

The locality is on the USGS Granite Peak 7¹/₂-min quadrangle map in NE¹/₄NE¹/₄ sec. 13 T37N R6W. It is reached by taking Middle Mountain Road from the northeast edge of Vallecito Reservoir to Tuckerville, and then south 1 mi to the mine. The tunnel is collapsed, but samples with microscopic crystals can be found sparingly on the small dump. All theisite needs to be tested with acid to distinguish it from aurichalcite.

Special thanks to Paul Hlava for his analysis.

Supplemental reading
Schmitt, L. J., and Raymond, W. H., 1977, Geology and mineral deposits of the Needle Mountains district, southwestern Colorado: U.S. Geological Survey, Bulletin 1434, 40 pp.

Smith, D. A., 1982, Song of the Hammer and Drill: Colorado School of Mines Press, pp. 174-175.

Steven, T. A., Schmitt, L. J., Jr., Sheridan, M. J., and Williams, F. E., 1969, Mineral resources of the San Juan Primitive
Area, Colorado: U.S. Geological Survey, Bulletin 1261-F, 113 pp.

Taggart, J. E., Jr., and Foord, E. E., 1980, Conichalcite, cuprian austinite, and plumbian conichalcite from La Plata
County, Colorado: Mineralogical Record, v. 11, no. 1, pp. 37-38.

Theis, N. J., Madson, M. E., Rosenlund, G. C., Reinhart, W. R., and Gardner, H. A., 1981, National Uranium Resource Evaluation, Durango quadrangle, Colorado: Bendix Field Engineering Corporation, Grand Junction, Colorado. Williams, S. A., 1982, Theisite, a new mineral from Colorado: Mineralogical Magazine, v. 46, no. 338, pp. 49-50.